Daewoo B20S-2 Specifications Systems Operation Testing & Adjusting Disassembly & Assembly
Also see for B20S-2: Disassembly/Assembly
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Power Train Testing And AdjustingProblem 4: Sparks at the commutator and/orrapid brush wear.Probable Cause:1. Worn brushes:Make a replacement of the brushes. See NewBrush Installation And Brush Inspection inTesting And Adjusting.2. Overheating (too much heat) of the traction motor:Check for an overload motor or a motor withdefects. See Armature Commutator Inspectionin Testing And Adjusting.Decrease the current limit (C/L) adjustments ifset too high. See the MicroController SystemOperation module.Test the plugging rate, if set too short it willcause arcing and wear at the brushes.The duty cycle is too heavy, change the dutycycle.3. Defective drive motor:See Armature Commutator Inspection in TestingAnd Adjusting.a. Commutator bars burnt in two or more positions at180° apart because:(1) Armature bars open.Make a replacement of the armature.(2) Motor was stalled against a heavy load whilepower discharged and caused the two bars, incontact with the brushes, to burn.NOTICEToo heavy a load can stall the motor, and result in afailure to the drive motor.(3) Short circuit in the armature.See Armature Tests in Testing And Adjusting.(4) Armature not in balance, out of round, off centeror with high commutator bars. This causes thebrushes to bounce (move up and down).Make sure the diameter is the same all the wayaround and is in center line with the shaft. SeeSpecifications.b. Dirty motor that has a metallic or carbon dust. thisdust is a conductor which causes electrical shorts,increase amp draw and decrease drive motoroutput:Remove any dirt with air pressure.c. Brush movement causes arcing and brush wear:Check the brush springs for cracks, andoverheat signs (blue).Compare spring force with a new brush spring.Check the brush holder for oversize (larger sizethan for brush).Replace the brush spring if necessary.d. Loose brush leads or motor bus bar connections.Loose cable connections at motor terminals.Results are:(1) High resistance and heating.(2) Faster brush wear.Check brushes for tight-connections.Replace the brushes if leads are loose inbrush material. Check all cable and wireconnections for tightness.e. Wrong grade of brushes installed that are notadaptable to the motor:Make sure all the brushes are of DAEWOOstandards. Do not use other brands of brushes.f. Possibly heavy working condition that causes toomuch motor heat and rapid brush wear:Make a replacement of the brushes and makesure the brushes are seated. See New BrushInstallation and Brush Inspection in Testing AndAdjusting.Check the brush springs for the correctinstallation and for the correct spring usage. Toostrong a spring rate will increase amperagedraw and brush wear rate.Prevent operation in stall condition. Excessive(too much) duty cycle which increases motortemperatures and rapid brush wear.4. Overload of the drive motor such as: towing loads,constant ramp operation, chiseling (hydraulicactions that are not practical) loads and dragging(pull or push loads on the ground) loads:Operator training for better working practices.Add an auxiliary cooling to the drive motors.5. Current limit (C/L) set too high that causes toomuch current consumption through motors in thetransistor range:Decrease the current limit (C/L) adjustment tothe correct setting, see the MicroControllerSystem Operation module.6. Drive motor, armature or field windings have adefect that results in high current draw at lowtorque output:See Armature Tests and Field Coil and TerminalTests in Testing And Adjusting.11 |
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